Color characteristics of dye-containing inks play an important role in the quality of the printed ink-jet image. Perceived color quality can be characterized using any one of several color space systems, such as CIELAB or Munsell, as is well known in the art. With respect to Munsell color space, a given color is defined using three terms, namely Hue, Value, and Chroma. With respect to CIELAB color space, a color is defined using three terms L*, a*, and b*. With this system, L* defines the lightness of a color, and it ranges from 0 to 100 (with 100 being white). Additionally, the terms a* and b*, together, define the hue, where a* ranges from a negative number (green) to a positive number (red), and b* ranges from a negative number (blue) to a positive number (yellow). Additional terms such as h° (hue angle) and C* (chroma) are used to further describe a given color. A single ink-jet ink of a first color that has good chroma, gamut, hue angle, and lightfastness is not always optimal for use with other colors. In other words, not only does an individual color, i.e., cyan, magenta, or yellow, have to have acceptable color qualities, but the ink-set in which it is used also plays a role in whether the ink-jet ink performs in an acceptable manner. Further, it is very difficult to formulate an ink or ink set that can be used to generate neutral grey along the entire L* range, e.g., where the a* and b* color values of the ink(s) are each very close to 0.
Accordingly, investigations continue into developing ink and ink set formulations that have acceptable color values.